NH-3140 - Fix incorrect mapping-by-code of many-to-many collection of elements when a column name matches a class name

Author: diegose

src/NHibernate.Test/MappingByCode/IntegrationTests/NH3140/Domain.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+
+namespace NHibernate.Test.MappingByCode.IntegrationTests.NH3140
+{
+	public class Foo
+	{
+		public virtual Guid Id { get; set; }
+		public virtual ICollection<Bar> Bars { get; set; }
+	}
+
+	public class Bar
+	{
+		public virtual Guid Id { get; set; }
+	}
+}

src/NHibernate.Test/MappingByCode/IntegrationTests/NH3140/Fixture.cs

@@ -0,0 +1,25 @@
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.MappingByCode.IntegrationTests.NH3140
+{
+	public class Fixture
+	{
+		[TestCase("DifferentFromBar")]
+		[TestCase("Bar")]
+		public void ExplicitColumnNameIsAlwaysMapped(string columnName)
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Foo>(cm => cm.Bag(x => x.Bars,
+			 							   bpm => { },
+										   cer => cer.ManyToMany(mtmm => mtmm.Column(columnName))));
+			var mapping = mapper.CompileMappingFor(new[] { typeof(Foo), typeof(Bar) });
+			var hbmClass = mapping.RootClasses.Single(x => x.Name == "Foo");
+			var hbmBag = hbmClass.Properties.OfType<HbmBag>().Single();
+			var hbmManyToMany = (HbmManyToMany)hbmBag.ElementRelationship;
+			Assert.AreEqual(columnName, hbmManyToMany.column);
+		}
+	}
+}

src/NHibernate.Test/NHibernate.Test.csproj

@@ -673,6 +673,8 @@
     <Compile Include="NHSpecificTest\NH2923\Models.cs" />
     <Compile Include="NHSpecificTest\NH2923\ExtraLazyFixture.cs" />
     <Compile Include="NHSpecificTest\NH3405\Fixture.cs" />
+    <Compile Include="MappingByCode\IntegrationTests\NH3140\Domain.cs" />
+    <Compile Include="MappingByCode\IntegrationTests\NH3140\Fixture.cs" />
     <Compile Include="NHSpecificTest\NH3428\Entity.cs" />
     <Compile Include="NHSpecificTest\NH3428\Fixture.cs" />
     <Compile Include="NHSpecificTest\NH3408\Fixture.cs" />

src/NHibernate/Mapping/ByCode/Impl/ManyToManyMapper.cs

@@ -44,16 +44,15 @@ public void Column(Action<IColumnMapper> columnMapper)
 			      	unique = manyToMany.unique,
 			      	uniqueSpecified = manyToMany.unique,
 			      };
-			string defaultColumnName = elementType.Name;
-			columnMapper(new ColumnMapper(hbm, defaultColumnName));
+			columnMapper(new ColumnMapper(hbm, Collection.DefaultElementColumnName));
 			if (ColumnTagIsRequired(hbm))
 			{
 				manyToMany.Items = new[] {hbm};
 				ResetColumnPlainValues();
 			}
 			else
 			{
-				manyToMany.column = defaultColumnName == null || !defaultColumnName.Equals(hbm.name) ? hbm.name : null;
+				manyToMany.column = Collection.DefaultElementColumnName.Equals(hbm.name) ? null : hbm.name;
 				manyToMany.unique = hbm.unique;
 			}
 		}